KOMPAS.com – Humans live on a planet called Earth that orbits the Sun in a galaxy called the Milky Way.
When humans began to think about whether there is other life beyond Earth, various research and space travel missions were carried out.
One of them is looking for the possibility of a planet outside the solar system or the Milky Way galaxy that is similar to Earth and can be inhabited by living things.
Most of the planets orbit other stars, but the free-floating exoplanets orbit the galactic center and are not attached to any stars.
Exoplanets are very difficult to see directly with a telescope. They are hidden by the bright light of the stars they orbit.
How do I Find Exoplanet?
Astronomers search for exoplanets by looking at the effect these planets have on the stars they orbit.
One way to find Exoplanets is to look for “wobbly” or swaying stars.
An orbiting planet causes the star to orbit slightly outside its center. From a distance, this makes it look like a swaying star.
Hundreds of planets have been discovered using this method. However, only large planets (Jupiter-sized or even larger) can be seen this way.
Smaller Earth-like planets are much harder to find because they only create tiny wobbles that are hard to detect.
Elements in the Exoplanet
Launch page Exoplanet Exploration NASA, Exoplanets consist of elements similar to the planets in the Milky Way. However, the mixture of the elements may be different.
Some planets are dominated by water or ice, while others are dominated by iron or carbon.
NASA has detected lava planets covered in molten oceans, swollen planets with a density like Styrofoam, and dense cores of planets still orbiting their stars.
How to find Earth-like planets in other solar systems?
In 2009, NASA launched a spacecraft called Kepler to search for exoplanets.
The Kepler spacecraft searches for planets of various sizes and orbits. These planets orbit around stars that vary in size and temperature.
Some of the planets discovered by Kepler are rocky planets that are at very special distances from their stars. This sweet spot is called the habitable zone, where life is possible.
Kepler detects exoplanets using something called the transit method. When a planet passes in front of its star, it is called a transit.
When a planet transits in front of a star, it blocks out some of the star’s light. That means the star will look slightly less bright when the planet passes in front of it.
Astronomers can observe how the star’s brightness changes during transit. This can help them figure out the size of the planet.
By studying the time between transits, astronomers can also tell how far the planet is from its star.
It can provide information about the planet’s temperature. If a planet has the right temperature, it can contain liquid water which is an essential ingredient for life.
What makes a planet habitable?
Citing pages NASA, A habitable planet is a planet that can sustain life for a significant period of time.
The main requirement according to the researchers is the presence of liquid water. Yet habitable planets result from a complex network of interactions between the planets themselves, the systems of which they are part, and the stars they orbit.
Launch Live Science, October 9, 2020, astronomers have discovered more than 4,000 exoplanets.
Most of these are not very conducive to life. For example, the planet KELT-9b is so hot that its atmosphere is constantly melting.
But there are also plenty of planets within their star’s habitable zone, or “just right” distances that are conducive to surface temperatures that aren’t too hot or too cold to evolve.
Researchers Schulze-Makuch and his colleagues examined habitable exoplanets. One of the conditions for being habitable according to them is a planet that has stars of the right size and life span.
That’s because it took complex life 3.5 billion years to evolve on Earth and 4 billion years for more advanced life like humans to emerge.
In addition, the planet is large, so there is more space for land and habitat. Larger planets will also have higher gravity and make the atmosphere thicker.
It would be beneficial for organisms that travel by flight.
Then another condition is a planet that is warmer than Earth. That means less polar regions, which are mostly barren.
But the warmer planet must also be wetter than Earth so that desert will not dominate the land.
It is also hoped that the planet will resemble Earth at the beginning of the Carboniferous, a period of about 359 million years ago, when most of the world’s land mass had a tropical rainforest climate. That’s because global warming is not good for life on Earth.
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